Epstein's square and circle method is stipulated by Chinese national standard (GB/T 3655-2000) as a method for detecting magnetic property of electric steel, which has strict requirements on weight, surface quality and so on of specimens. In the case that a specimen has too small weight and poor surface quality, it is impossible to use the Epstein's square and circle method to measure magnetic property (GB/T 3655-2000 requirements: effective mass of a specimen shall be at least 240 g, length of a specimen is recommended to be 300 mm, mass is about 1 kg; shear requirements of a specimen lie in that the shear shall be orderly, flat, being of good right-angle, and having no obvious burrs on the edge).
Etch pits are formed by preferential corrosion performed on crystal face of specimen surface. By use of this characteristic, it is possible to use metallographic etch-pit method to directly calculate crystallographic orientation of each crystal grain in the specimen (see “FORMATION CONDITIONS AND GEOMETRIC DIVERSITY OF ETCHED PITS”, Y. Luo, Acta metall Sin, 1982, 18 (4), p 472; “A STUDY ON THE DEFORMATION AND PRIMARY RECRYSTALLIZATION TEXTURE IN A MnS—AlN-INHIBITED 3% SILICON STEEL”, Q. C. Lv, R. J. Shuai, X. Y. Zhou et. al., Acta Metall Sin, 1981, 17 (1), p 58); “The application of the etch-pit method to quantitative texture analysis”, K. T. LEE, G. de WIT, A. MORA WIEC, J. A. SZPUNAR, JOURNAL OF MATERIAL SCIENCE, 1995, 30, p 1327-1332), and then to calculate orientation deviation angle θi of the crystal grain (see “ODF Determination of the Recrystallization Texture of Grain Oriented Silicon Steel from the Etch Figure”, G. Liu, F. Wang et. al., Journal of Northeastern University (Natural Science), 1997, 18 (6), p 614; “The application of the etch-pit method to quantitative texture analysis”, K. T. LEE, G. de WIT, A. MORA WIEC, J. A. SZPUNAR, JOURNAL OF MATERIAL SCIENCE, 1995, 30, p 1327-1332).
Magnetocrystalline anisotropy is a phenomenon due to a coupling effect between electron orbit and magnetic moment as one party and crystal lattice as another party, which makes magnetic moment have an optimum-choosing arrangement along a certain crystallographic axis, so as to result in difference of magnetization characteristics in various crystallographic axis directions. Crystallographic axis <100> is an easy magnetization direction, crystallographic axis <111> is a hard magnetization direction, and crystallographic axis <110> falls in between. As to oriented silicon steel, its electromagnetic property is closely related to crystal grain orientation <100> of a specimen (see “Electric Steel”, H E Zhongzhi, Metallurgical Industry Press, Beijing, 1996; “Mechanism of Orientation Selectivity of Secondary Recrystallization in Fe-3% Si Alloy”, Yoshiyuki USHIGAMI, Takeshi KUBOTA and Nobuyuki TAKAHASHI, Textures and Microstructures, vol. 32, p 137-151; “The Relationship between Primary and Secondary Recrystallization Texture of Grain Oriented Silicon Steel”, Tomoji KUMANO, Tsutomu HARATANI and Yoshiyuki USHIGAMI, ISIJ International, 2002, 42(4) 440). In view of the above, it is possible to use the metallographic pit-etching method plus calculation formula to take the place of magnetism-measuring devices to detect electromagnetic property of oriented silicon steel, as an innovative solution, which has the advantage that it can detect electromagnetic property in the cases that Epstein's square and circle method is not applicable thereto, such as specimen's weight being too small or its surface quality being poor.
In Chinese patent (Publication No.: CN101216440A), this invention utilizes a unsymmetrical X-ray diffraction method by using a fixed angle 2θ to perform ω can, in order to determine distribution of lattice orientation in the easy magnetization direction [001] of oriented silicon steel. A shortcoming of this patent, however, lies in that only deviation angle of lattice orientation [001] of the finished oriented silicon steel product is measured, but not further studying relativity between deviation angle of lattice orientation [001] and magnetism of the oriented silicon steel product.
In Chinese patent (Publication No.: CN101210947A), this invention measures three Euler angles of lattice orientation at every point of a specimen by use of EBSD system and accounts ratio X in every same or similar lattice orientation, and then calculates reckoned thickness coefficient fH, composition fC and influence coefficient e of orientation difference on performance. Magnetic property B of the specimen is obtained by correcting these coefficients based on pure iron performance Bθ. However, this patent has the following shortcomings: firstly, since EBSD device is expensive and is cumbersome in operation, many enterprises, especially small and medium-sized ones, are not able to apply this technique; secondly, with regards to calculation model for magnetic property of a finished product, it has been found from experimental data (oriented silicon steel with thickness 0.2˜0.3 mm) that thickness has little impact on magnetic property of the finished product, and it has been found from researches on chemical compositions that Si is a predominant influencing factor, and other chemical compositions have a little or basically no influence.